The subject of access control mechanisms in computer systems is concerned with effective means to protect the anonymity of private information on the one hand, and to regulate the access to shareable information on the other hand. Effective means for access control may be considered on three levels: memory, process and logical. This report is a review of the logical access control mechanisms implemented in two computer systems. The first system, PSF, is an on-line, multi-access operating system with an advanced data base management capability on an IBM 7040/PDP/8/DEC 338 coupled computer configuration. The second computer system, EDMF, is a time-sharing operating system with extended data base management capability on a RCA Spectra 70/46 virtual memory computer. (A related document is LI004414.) (Author/SJ)